Electric heater for use with automobiles



O. L. PEARD ET AL ELECTRIC HEATER FOR USE WITH AUTOMOBILES Re. 18,454 2 Sheets-Sheet 1 May 3, 1932.

Original Filed Dec. 23, 1929 O- L. PEARD ET AL ELECTRIC HEATER FOR USE WITH AUTOMOBILES Re. 18,454 2 Sheets-Sheet 2 May 3, 1932.

Original Filed Dec. 23, 1929 Reissuecl May 3, 1932 UNITED STATES OLIVER LEOPOLD PEABD AND STANLEY MCCLOUD PEABID, OF CROYDON, AND ALFRED FRANK HARRISON, OF EPSOM, ENGLAND ELECTRIC HEATER FOR USE WITH AUTOMOBILES Original No. 1,832,578, dated November 17, 1931, Serial No. 416,168, filed December 23, 1929. Application for reissue filed March 17, 1932. Serial No. 599,556.

This invention relates to an improved electric heater for use with automobiles.

It is well known that with extreme temperatures, the water in the cooling system of an automobile is liable to freeze and the cnsequent expansion may cause very considerable damage by cracking the cylinders or other parts of the internal combustion engine. Apart from the question of possible damage, there is also the disadvantage that in ver cold weather automobiles may become difli cult to start. It is well known to endeavour to avoid these disadvantages by providing so-called safety oil burning heaters of one kind or another in close proximity to the engine or radiator of an automobile. Said heaters, however, all suffer from more or less serious disadvantages. The heaters, which are in most common use, are those in which the heat is obtained from the burning of oil fuel, such as paraflin, and in such heaters the serious disadvantage occurs, that it obviously is undesirable to place a flame, even if enclosed in a protecting gauze, in close proximity to an automobile engine, owing to the danger of fire. Furthermore, such heaters are messy to fill and use.

It is a primary object of the present invention to provide a heater which may be placed in perfect safety in close proximity to the engine or radiator of an automobile.

further object is to provide a heater which is clean and simple to use and of robust and sturdy construction.

Another object is to provide a heater which will automatically maintain the engine of an automobile at or about the desired minimum temperature.

These and other objects are attained by employing for the purpose specified an electric heater comprising resistance windings of low specific resistance of such design that the heat necessary to maintain the automobile engine above apredetermined minimum temperature, is emitted at a comparatively low temperature well below the ignition point of petrol, the necessary heat transference being obtained by convection of air. Preferably, the circuit for the electric heater, includes a thermostat adapted to switch in the heater when the temperature of the surrounding air falls below the predetermined minimum allowable temperature, and to switch said heater out of circuit when the temperature rises above said predetermined minimum temperature.

The invention Will be better understood with reference to the accompanying drawings which show by way of example one form of the construction in accordance with the said invention.

In these drawings, Figure 1 is a perspective View showing a heater lay-out in accordance with the invention, said lay-out comprising the heater proper, a wall plug, a. fuse and a thermostatic switch, the whole being supplied from suitable mains. F igure 2 is a detail View showing in end section, one resistance coil arranged in a heater. Figure 3 is a section taken at right angles to Figure 2, and Figure 4 is a detail showing a preferred form of stamped perforated grid employed as top and bottom of the heater. Figure 5 is a. schematic and diagrammatic View showing the electrical connections of a heater consisting of four resistance windings.

Upon reference to the drawings, it will be seen that the heater lay-out comprises the heater proper H energized through the usual flexible lead FL from a wall plu WP. In circuit with the wall plug, is a use box F and a thermostatic switch TS of any known pattern. This switch forms per se no part of this invention, and as the construction thereof will be known to those skilled in the art, it is not thought necessary to describe it here. The thermostatic switch is preferably arranged to operate within limits of about 540 F. on and off, i. e. to close the current supply circuitof the heater (or of a number of heaters in the same circuit) when the temperature falls below F. (say), and to open said circuit, when it rises above F. (say). The outward appearance of the heater will be seen from Figure 1, said heater comprising a stamped or otherwise suitably formed metal pedestal-like frame 1, standing upon corner legs 2, and covered as to its top surface with a stamped perforated grille 3. Mounted within the member 1 is a subframe 4l made of stout material which .is a good thermal and electric insulator e. g. enamelled oak wood about thick which is held to the member 1 in any suitable way, for example, by means of screws, such as 5. The windings are of enamelled copper wire or aluminum or other low specific resistance material, and are wound over a double layer 0 of asbestos paper which is wrapped round a tube 7 preferably of hardrolled asbestos or other strong heat resisting material. These tubes, of which there may be any desired number depending upon the total wattage of the heater are held in place by hard wood plugs 8 pushed into the end of the tube and formed each with a central hole 9 for receiving a nail 10 driven into and through the sub frame. 11 is a fibre washer constituting a conveniently insulating and resilient distance piece between the tube and the sub frame. Connections from the copper wire (suitably ba'rcd of enamel) are taken to screws, such as 12, threaded into a brass ring 13 positioned in the small space left between the hard wood plug 8 and the tube 7. Leads are taken from screws 12 to a terminal box it carried by the sub-frame, and conveniently positioned, for example, in the space between two corner legs of the whole device. As above stated the number of resistance wound heatin tubes depends upon the wattage and also 0 course upon the voltage of the heater. For example, a 100 watt heater, for use with a 205 volt supply, may comprise three coils which are connected in series and are wound each upon a tube approximately 10% long. the winding length of each tube being ust under 9 there being about 140 turns per inch of enamelled copper wire of No. S. W. G. The total resistance of the tubes is of the order of 330 ohms at 60 F. For a 180 watt heater, it would be convenient to em ploy four coils, and for a 260 watt heater. 5 coils. These winding details are given by way of example only, and will. of course, vary in accordance with the design requirements.

In the examples given, however, the wattage per unit area of heating winding ex posed to air is sufliciently low to give an output temperature in normal circumstances of below 150 F. In order to prevent damage to the inside of the heater and to permit free flow of air, a grille 15, similar to that employed on the top of the heater, is fitted underneath, the terminal box being preferably mounted on this grille, as shown.

Overall dimensions of a heater such as described would be of the order of 13" x 6" x 5" high, the dimensions between the bottom of a leg and the top of the curved portion of the main frame between adjacent legs being about 2", i. e. the depth of the main frame between legs would be about 3".

In operation, air is drawn in from the grille beneath the heater winding, and is heated by direct contact with the windings and is then convected through the upper grille. A convenient way of utilizing the heater is to merely push the heater underneath the engine hood, so that the hot air rises from the heater and is more or less trapped under the said hood, thus maintaining the engine and radiator at not less than a desired minimum temperature.

It will be understood that the constructional details given in this specification are only by way of example, and to enable the invention readily to be carried into effect. They are not intended to be limiting in any way, since the said invention is obviously capable of wide modification in design, without departing from the spirit thereof.

Heaters according to this invention give an air temperature rise from ingoing to outcoming air of about 7 0 F. i. e. at a general temperature of 60 F. the emitted air is of the order of 130 F.-a temperature which is well below the ignition temperature of motor oil.

Heaters in accordance with this invention may conveniently be designed to deliver from, say 300 to 1,000 cubic feet per hour, according to size under the usual conditions of usage when surrounding air is near freezing point, the temperature of the copper coils is below 160 F. and air is discharged from the Convector at a temperature under 120 F. and at a velocity of less than %th feet per second. A large volume of slowly moving air at low temperature is thus furnished and is best adapted for the purpose of safely warming the automobile power system.

lVhat we claim is 1. An electric air warming apparatus for producing a large volume of slowly moving air at comparatively low temperature for maintaining warm the cooling system and other engine parts of the internal combustion engine of an automobile and adapted for use below the engine of an automobile, comprising in combination a shallow rectangular metal chamber having feet and having its upper and lower faces covered by grille plates having narrow slotted holes of large area to pass a large vertical air stream, an inner framework of nonconducting heat insulating material supported within said metal case and separating said case from the heatingelements proper and supporting the endsof said heating elements, and a plurality of heating elements supported within said insulating framework, said elements having airways therebetween and being constructed of closely wound low resistance material wound on long narrow heat resisting tubes, the resistance values of said elements relative to their energy consumption and heating area being so chosen that maximum temperature reached in working is only of the order of 180 F.

ta te-a 2. An electric air warming apparatus for producing a large volume of slowly moving air at comparatively low temperature for maintaining warm the cooling system and other engine parts of the internal combustion engine of an automobile and adapted for use below the engine of an automobile, comprising in combination a shallow rectangular metal chamber having feet and having its up per and lower faces covered by grille plates having narrow slotted holes of large area to pass a large vertical airstream, an inner frame work of wood supported within said metal case and separating said case from the heating elements proper and supporting the ends of said heating elements, and a plurality of heating elements supported within said woodcn frame work, said elements having airways therebetwvccn and being constructed of closely wound low resistance material wound on long narrow heat resisting tubes, the resistance values of said elements relative to their energy consumption and heating area being so chosen that maximum temperature reached in working is only of the order of 180 F.

3. An electric air warming apparatus for producing a large volume of slowly moving air at comparatively low temperature for maintaining warm the cooling system and other engine parts of the internal combustion engine of an automobile and adapted for use below the engine of an automobile, comprising in combination a shallow rectangular metal chamber having feet and having its upper and lower faces covered by grille plates having narrow slotted holes of large area to pass a large vertical air stream, an inner framework of nonconducting heat insulating material supported within said metal case and slap arating said case from the heating elements proper and supporting the ends of said heating elements, and a plurality of heating elements supported within said insulating framework in a row of a single tier, said elements having airways thercbetween and being constructed of closely wound low resistance material wound on long narrow heat resisting tubes, the resistance values of said elements relative to their energy consumption and heating area being so chosen that maximum temperature reached in working is only of the order of 180 F.

4. An electric air warming apparatus for producing a large volume of slowly moving air at comparatively low temperature for maintaining warm the cooling system and other engine parts of the internal combustion engine of an automobile and adapted for use below the engine of an automobile, comprising in combination a shallow rectangular metal chamber having feet and having its upper and lower faces covered by grille plates having narrow slotted holes of large area to pass a large vertical air stream, an inner framework of nonconducting heat insulating material supported within said metal case and separating said case from the heatin elements proper and supporting the ends 0 said heating elements, and a plurality of heating elements supported within said insulating framework in a row of a single tier, said elements having airways therebetween and being constructed of closely wound enamelled copper wire wound on asbestos paper wrapped around long and narrow heat resisting tubes, the resistance values of said elements relative to their energy consumption and heating area being so chosen that maximum temperature reached in working is only of the order of 180 F.

An electric air warming apparatus for producing a large volume of slowly moving air at compaatively low temperature for maintaining warm the cooling system and other engine parts of the internal combustion engine of an automobile and adapted for use below the engine of an automobile, comprising in combination a shallow rectangular metal chamber having feet and having its upper and lower faces covered by grille plates having narrow slotted holes of arge area to pass a large vertical air stream, an inner franmwork of nonconducting heat insulating material supported within said metal case and separating said case from the heating elements proper and supporting the ends of said heating elements, a plurality of heating elements supported within said insulating framework, said elements having airways therebctween and being constructed of closely wound low resistance material wound on long narrow heat resisting tubes, the resistance values of said elements relative to their energy consumption and heating area being so chosen that maximum temperature reached in working is only of the order of 180 F., a circuit extending from a source of electrical supply through said heating elements, and a thermostatic switch regulator in said circuit.

6. An electric air warming apparatus for producing a large volume of slowly moving air at comparatively low temperature for maintaining warm the cooling system and other engine parts of the internal combustion engine of an automobile and adapted for use below the engine of an automobile, comprising in combination a shallow rectangular metal chamber having feet and having its upper and lower faces covered by grille plates having narrow slotted holes of large area to pass a large vertical air stream, an inner framework of nonconducting heat insulating material supported within said metal case and separating said case from the heating elements proper and supporting the ends of said heating elements, a plurality of heating elements supported within said insulating framework in a row of a single tier, said elements having airways therebetween and being constructed of closely wound enamelled copper Wire Wound on asbestos paper wrapped around long and narrow heat resist ing tubes, the resistance values of said elements relative to their energy consumption and heating area being so chosen that maximum temperature reached in Working is only of the order of 180 F, a circuit extending from a source of electrical supply through said heating elements, and a thermostatic switch regulator in said circuit.

7. An electric low temperature Convector for warming the cooling system and other parts of internal combustion engines comprising in combination, low temperature heating elements of large surface area, an outer main protecting case of metal having perforated top and bottom grille plates, a sub-frame within said main protecting case, said sub frame being made of heat insulating and electrically insulating material, insulating tubes carried by said sub-frame, windings of enamelled copper wire wound on asbestos paper Wrapped upon said tubes, said windings constituting the heating members proper, and air passageways between said tubes, the resistance value of the heater relative to its energy consumption and surface area being so chosen that the maximum temperature reached by the copper windings is of the order of 160 F., the inlet air being at about 40 F., and the outlet air discharge being at approximately F.

8. An electric low temperature convcctor for warming the cooling system and other parts of internal combustion engines comprising in combination, low temperature heating elements of large surface area, an outer main protecting case of metal having perforated top and bottom grille plates, a sub-frame within said main protecting case, said sub-frame being made of heat insulating and electrically insulating material, in sulating tubes carried by said sub-frame, windings of enamelled copper wire wound on asbestos paper wrapped upon said tubes, said windings constituting the heating members proper, air passageways between said tubes, the resistance value of the heater relative to its energy consumption and surface area being so chosen that the maximum temperature reached by the copper windings is of the order of F., the inlet air being at about 40 F., the outlet air discharge being at approximately 120 F., and a circuit extending from a source of electrical supply to said convector and thermostatic switch regulator included in said circuit.

In testimony that we claim the foregoing as our invention, we have signed our names this 2d and 4th days of March, 1932.

OLIVER LEOPOLD PEARD. STANLEY MCCLOUD PEARD. ALFRED FRANK HARRISON.

CERTIFICATE OF CORREGTIUN.

Reissue No. 18,454. May 3, 1932.

OLIVER LEOPOLD PEARD ET AL.

lt is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 90, for the word "oil" read fuel; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 1st day of November, A. D. 1932.

M. J. Moore,

(Seal) Acting Commissioner of Patents. 

